JP5028930B2 - Focus detection apparatus and imaging apparatus - Google Patents

Description

  The present invention relates to a focus detection apparatus and an imaging apparatus.

  An image sensor equipped with a focus detection pixel consisting of a microlens and a pair of light-receiving units located behind it is placed on the planned focal plane of the optical system, and the focus adjustment state of the optical system is detected by the pupil division phase difference detection method. A focus detection apparatus is known (for example, see Patent Document 1).

Prior art documents related to the invention of this application include the following.
JP 2005-148091 A

In the above-described embodiment, the center of gravity of the focus detection light beam passing through the pair of regions due to vignetting is calculated based on the exit window information of the optical system, the focus detection position information, and the received light intensity distribution of the photoelectric conversion unit, and based on the center of gravity interval. To calculate the defocus amount.
However, when trying to increase the accuracy of the center-of-gravity distance by such a method, enormous data of the optical system and complicated arithmetic processing are required, and it is difficult to cope with various optical systems having different configurations.

According to a first aspect of the present invention, there is provided a focus detection apparatus including a first pair of images formed by a first pair of light beams respectively passing through a first pair of regions of an exit pupil of an optical system, and an exit of the optical system. A second pair of images formed by a second pair of luminous fluxes respectively passing through the second pair of pupil regions, respectively, and receiving the first pair of images and the second pair of images, respectively. A first light receiving means for outputting a corresponding first pair of image signals and a second pair of image signals, a first image shift amount and a second pair of image signals based on the first pair of image signals; A first image displacement amount detecting means for detecting a second image displacement amount based on the image signal; a center-of-gravity interval between the second pair of regions; the first image displacement amount; and the second image displacement amount. A first center-of-gravity interval calculation unit that calculates a center-of-gravity interval of the first pair of regions based on the amount; and Defocus amount calculation means for calculating a defocus amount based on the calculated centroid interval and the first image shift amount, and the centroid interval between the first pair of regions It is characterized by being larger than the distance between the centers of gravity of the two pairs of regions.
A focus detection apparatus according to a seventh aspect of the invention receives a pair of images formed by a pair of light beams passing through a pair of regions of an exit pupil of an optical system, and outputs a pair of image signals corresponding to the pair of images. A light receiving means; a diaphragm control means for controlling the diaphragm aperture of the optical system to at least a first aperture diameter and a second aperture diameter smaller than the first aperture diameter; and A first image shift amount is detected based on the pair of image signals when the first aperture diameter is controlled, and when the aperture opening is controlled to the second aperture diameter by the aperture control means. An image shift amount detecting means for detecting a second image shift amount based on the pair of image signals, a center-of-gravity distance between the pair of regions when the stop aperture is controlled to the second aperture diameter, and the first Based on the image shift amount of the second image shift amount and the second image shift amount. A center-of-gravity interval calculating unit that calculates a center-of-gravity interval between the pair of regions when the aperture is controlled to the first aperture diameter; and the center-of-gravity interval calculated by the center-of-gravity interval calculating unit and the first image shift. And a defocus amount calculating means for calculating a defocus amount based on the amount.
According to an eighth aspect of the present invention, there is provided a focus detection apparatus including a first focus detection area extending in a radial direction from the center of the photographing screen at a position separated from the center of the photographing screen by a predetermined distance within the photographing screen of the optical system. A focus detection device having a second focus detection area extending perpendicular to the focus detection area of the optical system, arranged in a direction corresponding to the first focus detection area, Each of the first pair of images formed by the first pair of light fluxes passing through each of the pair of regions is received, and a first pair of image signals corresponding to the first pair of images is output. A first focus detection pixel array and a second pair of light fluxes arranged in a direction corresponding to the second focus detection area and respectively passing through a second pair of regions of the exit pupil of the optical system. Receiving a second pair of images respectively, A first light receiving means having a second focus detection pixel column for outputting a second pair of image signals corresponding to the pair of images, and a first image shift amount based on the first pair of image signals; A first image displacement amount detecting means for detecting a second image displacement amount based on the second pair of image signals, a center-of-gravity interval between the second pair of regions, and the first image displacement amount; Based on the second image shift amount, a first centroid interval calculating unit that calculates a centroid interval between the first pair of regions, the centroid interval calculated by the first centroid interval calculating unit, and the Defocus amount calculation means for calculating a defocus amount based on the second image shift amount.

  According to the present invention, it is possible to accurately obtain a conversion coefficient for converting an image shift amount into a defocus amount with a simple calculation without requiring enormous data and complicated calculation processing of the optical system. It is possible to easily cope with various optical systems having different configurations.

  An example in which the imaging apparatus according to an embodiment of the present invention is applied to a digital still camera will be described. FIG. 1 shows the configuration of an embodiment. A digital still camera 201 according to an embodiment includes an interchangeable lens 202 and a camera body 203, and the interchangeable lens 202 is attached to the camera body 203 by a mount unit 204.

  The interchangeable lens 202 includes a lens drive control device 206, a zooming lens 208, a lens 209, a focusing lens 210, a diaphragm 211, and the like. The lens drive control device 206 includes peripheral components such as a microcomputer and a memory. The lens drive control device 206 controls driving of the focusing lens 210 and the aperture 211, detects the state of the aperture 211, the zooming lens 208 and the focusing lens 210, and body drive control described later. Transmission of lens information to the device 214 and reception of camera information are performed.

  The camera body 203 includes an imaging element 212, a body drive control device 214, a liquid crystal display element drive circuit 215, a liquid crystal display element 216, an eyepiece lens 217, a memory card 219, and the like. Pixels, which will be described later, are arranged in a two-dimensional manner on the imaging element 212, and are arranged on the planned imaging plane of the interchangeable lens 202 to capture a subject image formed by the interchangeable lens 202. Although details will be described later, focus detection pixels are arranged at predetermined focus detection positions of the image sensor 212.

  The body drive control device 214 includes a microcomputer and peripheral components such as a memory. The body drive control device 214 reads the image signal from the image sensor 212, corrects the image signal, detects the focus adjustment state of the interchangeable lens 202, and outputs from the lens drive control device 206. It receives lens information, transmits camera information (defocus amount), and controls the operation of the entire digital still camera. The body drive control device 214 and the lens drive control device 206 communicate via the electrical contact portion 213 of the mount portion 204 to exchange various information.

  The liquid crystal display element driving circuit 215 drives a liquid crystal display element 216 of an electronic viewfinder (EVF: electric viewfinder). The photographer can observe an image displayed on the liquid crystal display element 216 via the eyepiece lens 217. The memory card 219 is removable from the camera body 203 and is a portable storage medium that stores and stores image signals.

  The subject image formed on the image sensor 212 through the interchangeable lens 202 is photoelectrically converted by the image sensor 212 and the output is sent to the body drive controller 214. The body drive control device 214 calculates a defocus amount at a predetermined focus detection position based on the output data of the focus detection pixels on the image sensor 212, and sends this defocus amount to the lens drive control device 206. The body drive control device 214 stores an image signal generated based on the output of the image sensor 212 in the memory card 219 and sends the image signal to the liquid crystal display element drive circuit 215 to display an image on the liquid crystal display element 216. Let

  The camera body 203 is provided with operation members (not shown) (shutter buttons, focus detection position setting members, etc.), and the body drive control device 214 detects operation state signals from these operation members. The corresponding operations (imaging operation, focus detection position setting operation, image processing operation) are controlled.

  The lens drive control device 206 changes the lens information according to the focusing state, zooming state, aperture setting state, aperture opening F value, and the like. Specifically, the lens drive control device 206 monitors the positions of the lenses 208 and 210 and the diaphragm position of the diaphragm 211, calculates lens information according to the monitor information, or monitors from a lookup table prepared in advance. Select lens information according to the information. The lens drive control device 206 calculates a lens drive amount based on the received defocus amount, and drives the focusing lens 210 to a focal point by a drive source such as a motor (not shown) based on the lens drive amount.

  FIG. 2 shows a focus detection position on the imaging screen, that is, a region (focus detection area) where a subject image is sampled on the shooting screen when a focus detection pixel row described later performs focus detection. Focus detection areas 101 and 102 are arranged on the left and right in the horizontal direction across the center on the imaging screen 100. Focus detection pixels are linearly arranged in the longitudinal direction of the focus detection areas 101 and 102 indicated by rectangles. The two focus detection areas 101 and 102 are located on a circumference 103 having a predetermined radius centered on the center of the screen.

  FIG. 3 is a front view showing a detailed configuration of the image sensor 212, and is an enlarged view of the vicinity of one focus detection area on the image sensor 212. The imaging element 212 includes an imaging pixel 310, a first focus detection pixel 311, and a second focus detection pixel 312. As shown in FIG. 4, the imaging pixel 310 includes a microlens 10, a photoelectric conversion unit 11, and a color filter (not shown). There are three types of color filters, red (R), green (G), and blue (B), and the respective spectral sensitivities are as shown in FIG. An imaging pixel 310 having each color filter is arranged in a Bayer array.

  The first focus detection pixel 311 includes a microlens 10 and a pair of photoelectric conversion units 12 and 13 as shown in FIG. The second focus detection pixel 312 includes a microlens 10 and a pair of photoelectric conversion units 14 and 15 as shown in FIG. The first focus detection pixel 311 and the second focus detection pixel 312 are not provided with a color filter in order to increase the amount of light, and the spectral characteristics thereof are the spectral sensitivity of a photodiode that performs photoelectric conversion, and the infrared cut filter (not shown). Spectral characteristics (see FIG. 8) are obtained by combining the spectral characteristics. This spectral characteristic is a spectral characteristic obtained by adding the spectral characteristics of the green pixel, the red pixel, and the blue pixel shown in FIG. 7, and the light wavelength region of the sensitivity is the light wavelength region of the sensitivity of the green pixel, the red pixel, and the blue pixel. It is comprehensive.

  The photoelectric conversion unit 11 of the imaging pixel 310 is designed in such a shape that the microlens 10 receives all the light beams that pass through the exit pupil (for example, F1.0) of a bright interchangeable lens. On the other hand, the pair of photoelectric conversion units 12 and 13 of the first focus detection pixel 311 are designed so that the microlens 10 receives all the light beams passing through a specific exit pupil (for example, F2.8) of the interchangeable lens. Is done. The pair of photoelectric conversion units 14 and 15 of the second focus detection pixel 312 is darker in the arrangement direction of the photoelectric conversion units than the pair of photoelectric conversion units 12 and 13 of the first focus detection pixel 311 by the microlens 10. The shape is designed so as to receive the light beam passing through (F8).

  As shown in FIG. 3, the imaging pixels 310 arranged in a two-dimensional manner are provided with color filters of RGB Bayer arrangement. The first focus detection pixels 311 and the second focus detection pixels 312 are densely arranged linearly without gaps in the rows where the B and G of the imaging pixels 310 are to be arranged. By disposing the first focus detection pixel 311 and the second focus detection pixel 312 in the row where B and G of the imaging pixel 310 are to be disposed, the first focus detection pixel 311 and the second focus detection pixel are performed by pixel interpolation described later. When the pixel signal at the position 312 is corrected, even if there is some error, it can be made inconspicuous to the human eye. This is because red is more sensitive to human eyes than blue, and the density of green pixels is higher than that of blue and red pixels, so the contribution of a green pixel to a single pixel defect is small. The first focus detection pixel 311 and the second focus detection pixel 312 are arranged in parallel to the center of the focus detection area.

  FIG. 9 shows a cross section of the imaging pixel 310. In the imaging pixel 310, the microlens 10 is disposed in front of the photoelectric conversion unit 11 for imaging, and the photoelectric conversion unit 11 is projected forward by the microlens 10. The photoelectric conversion unit 11 is formed on the semiconductor circuit substrate 29. A color filter (not shown) is disposed between the microlens 10 and the photoelectric conversion unit 11.

  FIG. 10 shows a cross section of the first focus detection pixel 311 and the second focus detection pixel 312. In the first focus detection pixel 311 (second focus detection pixel 312), the microlens 10 is disposed in front of the focus detection photoelectric conversion units 12 and 13 (14, 15), and the microlens 10 causes the photoelectric conversion unit 12, 13 (14, 15) is projected forward. The photoelectric conversion units 12 and 13 (14 and 15) are formed on the semiconductor circuit substrate 29. A filter (not shown) is disposed between the microlens 10 and the photoelectric conversion units 12 and 13 (14 and 15).

  Next, a focus detection method based on a pupil division method using a microlens will be described with reference to FIG. In FIG. 11, reference numeral 90 denotes an exit pupil set at a distance d in front of the microlens arranged on the planned imaging plane of the interchangeable lens. Here, the distance d is a distance determined according to the curvature and refractive index of the microlens, the distance between the microlens and the photoelectric conversion unit, and is hereinafter referred to as a distance measuring pupil distance. The distance measuring pupil distance d is set so as to match the average position of the exit pupil plane of the interchangeable lens group or a position in the vicinity thereof.

  Reference numeral 91 denotes an optical axis of the interchangeable lens, 50 and 60 are microlenses, 52 and 53 and 62 and 63 are photoelectric conversion units of a pair of focus detection pixels, and 72, 73, 82, and 83 are focus detection light beams. Reference numeral 92 denotes an area of the photoelectric conversion units 52 and 62 projected by the microlenses 50 and 60 (referred to as a distance measuring pupil), and 93 denotes an area of the photoelectric conversion units 53 and 63 projected by the microlenses 50 and 60 (measurement). Distance pupil).

  In FIG. 11, a focus detection pixel (consisting of a microlens 50 and a pair of photoelectric conversion units 52 and 53) on the optical axis 91 and an adjacent focus detection pixel (a microlens 60 and a pair of photoelectric conversion units 62, 63). In other focus detection pixels as well, the pair of photoelectric conversion units receive light beams that arrive at the microlenses from the pair of distance measuring pupils. The arrangement direction of the focus detection pixels is made to coincide with the arrangement direction of the pair of distance measuring pupils.

  The microlenses 50 and 60 are disposed in the vicinity of the planned imaging plane of the optical system, and the shape of the pair of photoelectric conversion units 52 and 53 disposed behind the microlens 50 disposed on the optical axis 91 is formed. Projection is performed on an exit pupil 90 separated from the microlenses 50 and 60 by a projection distance d, and the projection shape forms distance measurement pupils 92 and 93. Further, the microlens 60 disposed away from the optical axis 91 projects the shape of the pair of photoelectric conversion units 62 and 63 disposed behind the microlens 60 onto the exit pupil 90 separated by the projection distance d. The shape forms distance measuring pupils 92 and 93. That is, the projection direction of each pixel is determined so that the projection shape (ranging pupils 92 and 93) of the photoelectric conversion unit of each focus detection pixel matches on the exit pupil 90 at the projection distance d0.

  The photoelectric conversion unit 52 passes through the distance measuring pupil 92 and outputs a signal corresponding to the intensity of the image formed on the microlens 50 by the focus detection light beam 72 directed to the microlens 50. The photoelectric conversion unit 53 passes through the distance measuring pupil 93 and outputs a signal corresponding to the intensity of the image formed on the microlens 50 by the focus detection light beam 73 directed to the microlens 50. The photoelectric conversion unit 62 outputs a signal corresponding to the intensity of the image formed on the microlens 60 by the focus detection light beam 82 passing through the distance measuring pupil 92 and directed to the microlens 60. The photoelectric conversion unit 63 outputs a signal corresponding to the intensity of the image formed on the microlens 60 by the focus detection light beam 83 passing through the distance measuring pupil 93 and directed to the microlens 60.

  A large number of such focus detection pixels are arranged in a straight line, and the output of the pair of photoelectric conversion units of each pixel is collected into an output group corresponding to the distance measurement pupil 92 and the distance measurement pupil 93, thereby Information on the intensity distribution of the pair of images formed on the focus detection pixel array by the focus detection light fluxes that pass through the distance measuring pupil 93 is obtained. By applying image shift detection calculation processing (correlation calculation processing and phase difference detection processing) to be described later to this information, the image shift amounts of a pair of images are detected by a so-called pupil division phase difference detection method. Further, by performing a conversion operation according to the center-of-gravity interval of the pair of distance measuring pupils on the image shift amount, the current imaging plane with respect to the planned imaging plane (the focal point corresponding to the position of the microlens array on the planned imaging plane) The deviation (defocus amount) of the imaging plane at the detection position is calculated.

  In the above description, the distance measurement pupil is described as being not limited by the aperture opening, but in reality, the distance detection pupil is limited by the aperture opening and other aperture limiting elements (lens outer shape, hood, etc.) It becomes size.

  12 and 13 are front views showing the projection relationship of the photoelectric conversion unit on the exit pupil plane. In FIG. 12, the circumscribed circle of the distance measuring pupils 922 and 933 obtained by projecting the pair of photoelectric conversion units 12 and 13 from the first focus detection pixel 311 (see FIG. 5) onto the exit pupil plane 90 by the microlens is from the imaging plane. When viewed, a predetermined aperture F value (referred to as a distance measuring pupil F value, here F2.8) is obtained. A region 901 indicated by a broken line indicates a region corresponding to an aperture value having an aperture diameter larger than the aperture value F2.8, for example, F2, and includes the distance measuring pupils 922 and 933 therein.

  The distance G1 between the centroids 952 and 953 of the light beams (focus detection light beams) passing through the distance measuring pupils 922 and 933 in the direction in which the distance measuring pupils 922 and 933 are aligned (horizontal direction in the figure) passes through the distance measuring pupils 922 and 933. When the amount of image misalignment (the amount of misalignment in the plane perpendicular to the optical axis) of a pair of images formed on the intended focal plane by the light beam (focus detection beam) is converted into the amount of misalignment in the optical axis direction (defocus amount) Conversion parameters. When the aperture value of the interchangeable lens becomes larger than the distance measuring pupil F value 2.8, the center-of-gravity distance G1 of the pair of focus detection light beams changes. Further, when the position of the focus detection area is in the periphery of the screen, the focus detection light beam is limited by an aperture limiting element other than the stop, and the center-of-gravity interval G1 of the pair of focus detection light beams changes.

  On the other hand, in FIG. 13, the circumscribed circles of the distance measuring pupils 924 and 935 obtained by projecting the pair of photoelectric conversion units 14 and 15 from the second focus detection pixel 312 (see FIG. 6) onto the exit pupil plane 90 by the microlens 10 are connected. A predetermined aperture F value is obtained when viewed from the image plane. This aperture F value corresponds to the width of the distance measuring pupil in the direction in which the distance measuring pupils are arranged, and is hereinafter referred to as the distance measuring pupil F value. In this embodiment, it is F8. A region 901 indicated by a broken line indicates a region corresponding to an aperture value having an aperture diameter larger than the aperture value F2.8, for example, F2, and includes the distance measuring pupils 924 and 935 therein.

  The distance G2 between the centroids 952 and 953 of the light beams (focus detection light beams) passing through the distance measurement pupils 924 and 935 in the direction in which the distance measurement pupils 924 and 935 are arranged (horizontal direction in the figure) passes through the distance measurement pupils 924 and 935. When the amount of image misalignment (the amount of misalignment in the plane perpendicular to the optical axis) of a pair of images formed on the intended focal plane by the light beam (focus detection beam) is converted into the amount of misalignment in the optical axis direction (defocus amount) Conversion parameters. When the aperture value of the interchangeable lens is smaller than the distance measuring pupil F value 8, the center-of-gravity interval G2 between the pair of focus detection light beams is constant. Further, since the distance measurement pupil F value is large, even when the position of the focus detection area is in the periphery of the screen, the focus detection light beam is not limited by the aperture limiting element other than the diaphragm, and the center-of-gravity interval G2 of the pair of focus detection light beams does not change. .

  FIG. 14 shows the intensity distribution (light quantity) of the image signal of the focus detection pixel at the focus detection position around the screen on the vertical axis and the position of the focus detection pixel on the horizontal axis. When vignetting does not occur in the focus detection light beam, the pair of image data 400 and 401 are obtained by simply shifting the same image data waveform horizontally as shown in FIG. When the vignetting occurs in the focus detection light beam, the amount of the focus detection light beam passing through the distance measuring pupil changes depending on the focus detection position and the position deviation within the focus detection position, and the pair of image data 402 and 403 is shown in FIG. Thus, the same data is not relatively shifted.

  FIG. 15 is a flowchart showing the operation of the digital still camera (imaging device) shown in FIG. When the camera is turned on in step 100, the body drive control unit 214 repeatedly executes the operations in and after step 110. In step 110, aperture control according to a shooting aperture value automatically determined according to the field luminance measured by a photometry device (not shown) or manually set by a user using an operation member (not shown). Information is sent to the lens drive controller 206, and the aperture diameter is set to the photographing aperture value. Further, the image pickup pixel data is read out with this aperture diameter, and displayed on the electronic viewfinder.

  In step 120, data is read from the focus detection pixel array corresponding to the selected focus detection area in a state where the aperture diameter is set to the photographing aperture value. The focus detection area is selected by the user by operating a selection member (not shown). In step 130, an image shift detection calculation process (correlation calculation process), which will be described later, is performed based on a pair of image data read from the focus detection pixel array, an image shift amount is calculated, and a defocus amount is further calculated. In step 140, it is determined whether or not the focus is close, that is, whether or not the calculated absolute value of the defocus amount is within a predetermined value.

  If it is determined that it is not near the focus, the process proceeds to step 150, the defocus amount is transmitted to the lens drive control device 206, the focusing lens 210 of the interchangeable lens 202 is driven to the focus position, and the process returns to step 110 to perform the above operation. repeat. Even when focus detection is impossible, the process branches to this step, a scan drive command is transmitted to the lens drive control device 206, and the focusing lens 210 of the interchangeable lens 202 is driven to scan from infinity to the closest position, and the process returns to step 110. Repeat the above operation.

  On the other hand, if it is determined that the focus is close, the process proceeds to step 160, where it is determined whether a shutter release has been performed by operating a release button (not shown), and if it is determined that the shutter release has not been performed, the process returns to step 110. Repeat the above operation. On the other hand, if it is determined that the shutter release has been performed, the process proceeds to step 170, where aperture control information is transmitted to the lens drive control unit 206, and the aperture value of the interchangeable lens 202 is set to the photographing aperture value. When the aperture control is completed, the image sensor 212 performs an imaging operation, and image data is read from the image pickup pixel 301 and all the focus detection pixels 311 and 312 of the image pickup element 212.

  In step 180, the pixel data at each pixel position in the focus detection pixel array is interpolated based on the focus detection pixel data and the surrounding imaging pixel data. In the subsequent step 190, image data composed of the imaged pixel data and the interpolated data is stored in the memory card 219, and the process returns to step 110 to repeat the above operation.

  FIG. 16 is a flowchart showing details of the image shift amount calculation processing in step 130 of FIG. In step 200, the data of the first focus detection pixel row and the data of the second focus detection pixel row in the focus detection area 101, the data of the first focus detection pixel row and the data of the second focus detection pixel row in the focus detection area 102 are displayed. On the other hand, focus detection calculation processing (correlation calculation processing) is performed, and the image shift amount x11 corresponding to the data of the first focus detection pixel row in the focus detection area 101 and the data of the second focus detection pixel row in the focus detection area 101 are respectively obtained. The corresponding image shift amount x12, the image shift amount x21 corresponding to the data of the first focus detection pixel row in the focus detection area 102, and the image shift amount x22 corresponding to the data of the second focus detection pixel row in the focus detection area 101 are calculated. To do.

Here, focus detection calculation processing (correlation calculation processing) will be described. FIG. 17 is a flowchart showing details of the focus detection calculation process in step 200 of FIG. In step 300, focus detection calculation processing (correlation calculation processing) is started. In step 310, (1 to α1 for a pair of data sequences (α1 to αM, β1 to β: M is the number of data) output from the focus detection pixel sequence. ) To generate a first data string and a second data string (A1 to AN, B1 to BN). By this high frequency cut filter processing, noise components and high frequency components that adversely affect the correlation processing can be removed from the data string. Note that the processing in step 310 can be omitted when the calculation time is to be shortened or when it is already known that there is a small amount of high-frequency components since the focus has been greatly defocused.
An = αn + 2, αn + 1 + αn + 2,
Bn = βn + 2 · βn + 1 + βn + 2 (1)
In the formula (1), n = 1 to N.

In step 320, the correlation calculation shown in the equation (2) is performed on the data strings An and Bn, and the correlation amount C (k) is calculated.
C (k) = Σ | An · Bn + 1 + k−Bn + k · An + 1 | (2)
In equation (2), Σ operations are accumulated for n. Further, the range taken by n is limited to a range in which data of An, An + 1, Bn + k, and Bn + 1 + k exist according to the shift amount k. The shift amount k is an integer and is a relative shift amount with the data interval of the data string as a unit. The correlation calculation of equation (2) enables accurate image shift detection even when there is a gain difference between the two data strings (see FIG. 14B).

In step 330, the calculation result of the above equation (2) is obtained as shown in FIG. 18A when the correlation amount C is obtained when the pair of data has a high correlation amount (k = kj = 2 in FIG. 18A). (k) becomes the minimum (the smaller the value, the higher the degree of correlation). The shift amount x that gives the minimum value C (k) with respect to the continuous correlation amount is obtained using the three-point interpolation method shown in the equations (3) to (6).
x = kj + D / SLOP (3),
C (k) = C (kj) − | D | (4),
D = {C (kj-1) -C (kj + 1)} / 2 (5),
SLOP = MAX {C (kj + 1) -C (kj)), C (kj-1) -C (kj)} (6)

  Whether or not the shift amount x calculated by the equation (3) is reliable is determined as follows. As shown in FIG. 18B, when the degree of correlation between a pair of data is low, the value of the minimal value C (x) of the interpolated correlation amount is large. Accordingly, when C (x) is equal to or greater than a predetermined threshold value, it is determined that the calculated shift amount has low reliability, and the calculated shift amount x is canceled. Alternatively, in order to normalize C (x) with the contrast of data, when the value obtained by dividing C (x) by SLOP that is proportional to the contrast is equal to or greater than a predetermined value, the reliability of the calculated shift amount Is determined to be low, and the calculated shift amount x is canceled. Alternatively, when SLOP that is a value proportional to the contrast is equal to or less than a predetermined value, it is determined that the subject has low contrast and the reliability of the calculated shift amount is low, and the calculated shift amount x is canceled.

  As shown in FIG. 18C, when the correlation between the pair of data is low and there is no drop in the correlation amount C (k) between the shift ranges kmin to kmax, the minimum value C (x) is obtained. In such a case, it is determined that the focus cannot be detected. In step 340 of FIG. 17, the focus detection calculation process (correlation calculation process) is terminated and the process returns.

Note that the correlation amount C (k) may be calculated in step 320 by performing the correlation calculation shown in the following equation (7) or (8).
C (k) = Σ | An / An + 1−Bn + k / Bn + 1 + k | (7)
In equation (7), the Σ operation is accumulated for n. Further, the range taken by n is limited to a range in which data of An, An + 1, Bn + k, and Bn + 1 + k exist according to the shift amount k.
C (k) = Σ | An−Bn + k | (8)
In the equation (8), the Σ operation is accumulated for n. Further, the range taken by n is limited to a range in which data of An and Bn + k exist according to the shift amount k.

  Returning to FIG. 16 again, the description will be continued. In step 210, based on the four image shift amounts x11, x12, x21, x22, the center of gravity G1 of the distance measuring pupils 922, 933 corresponding to the first focus detection pixels shown in FIG. 'And.

  Here, the relationship among the center-of-gravity interval of the distance measurement pupil, the image shift amount, and the defocus amount will be described. 19 and 20 are front views showing a pair of photoelectric conversion unit projection relationships on the exit pupil plane. In FIG. 12 and FIG. 13, distance measurement pupils 922 and 933 corresponding to the first focus detection pixel 311 (see FIG. 5) and distance measurement pupils 924 and 935 corresponding to the second focus detection pixel 312 (see FIG. 6) are shown. The area 901 corresponding to the aperture opening of the interchangeable lens was not removed. 19 and 20, distance measuring pupils 922 and 933 corresponding to the first focus detection pixel 311 (see FIG. 5) and distance measurement pupils 924 and 935 corresponding to the second focus detection pixel 312 (see FIG. 6) are provided. In addition, a state in which the aperture is set by a region 902 corresponding to the aperture opening of the interchangeable lens having a large aperture F value is illustrated.

  In FIG. 19, the area 902 is smaller than the circumscribed circle of the distance measurement pupils 922 and 933 (the aperture value corresponding to the size of the area 902 is larger than the distance detection pupil F value of the first focus detection pixel), and the area 902 The distance between the centroids 962 and 963 of the light beam (focus detection light beam) passing through the distance measuring pupils 922 and 933 limited by is G1 ′.

  In FIG. 20, the distance G2 between the centroids 954 and 955 of the light beam (focus detection light beam) passing through the distance measuring pupils 924 and 935 limited by the region 902 has an aperture value corresponding to the size of the region 902 as the second focus detection. When the distance measurement pupil F value of the pixel is smaller, there is no change compared to the case where the distance measurement pupils 924 and 935 are not provided.

  FIG. 21 is a diagram for explaining vignetting of the distance measuring pupil around the screen. FIGS. 19 and 20 show a case where vignetting occurs in the distance measuring pupil simply because the aperture diameter of the exit pupil plane 90 is reduced. However, in addition to the aperture diameter becoming smaller, vignetting occurs in the distance measuring pupil. May occur. As shown in FIG. 21, when the position of the focus detection area is in S around the screen set to the planned focal plane P0, vignetting occurs in the distance measuring pupils 92 and 93 due to the aperture diameter of the exit pupil plane 90. Although there is no vignetting, the distance measuring pupil 92 is vignetted by the aperture limiting element 98 existing on the surface 99 farther from the exit pupil surface 90.

  22 and 23 are front views showing the projection relationship of the exit pupil plane in the state shown in FIG. 22 and 23 show a state in which a region 903 corresponding to the opening restricting element 98 is added to the state shown in FIGS. 12 and 13. In FIG. 22, the distance measuring pupil 922 is positioned by the area 903, and the center of gravity 972 of the light beam (focus detection light beam) passing through the distance measuring pupil 922 restricted by the area 903 is greater than the center of gravity 952 when not being positioned. It depends on the center. On the other hand, the distance measuring pupil 933 is not displaced by the region 903, and the position of the center of gravity 953 of the light beam (focus detection light beam) passing through the distance measuring pupil 922 does not change. Therefore, the distance between the distance measurement pupil centroids 972 and 953 is a centroid distance G1 'narrower than the centroid distance G1 when no vignetting occurs.

  In FIG. 23, since the distance measurement pupil F value is large, the area 903 causes no vignetting in the distance measurement pupils 924 and 935. Accordingly, the distance G2 between the centroids 954 and 955 of the light beam (focus detection light beam) passing through the distance measuring pupils 924 and 935 does not change.

  FIG. 24 is a diagram showing a relationship between the distance measurement pupil center of gravity interval and the image shift amount. In the exit pupil plane 90 in front of the planned focal plane P0, when the pair of focus detection light fluxes having the distance measurement center of gravity G1 ′ is focused on the plane P3 in front of the planned focal plane P0 d0, The amount of image shift at the focal plane P0 is x1. On the other hand, in the exit pupil plane 90, when the pair of focus detection light fluxes that are the distance measurement pupil center-of-gravity interval G2 is focused on the plane P3 that is in front d0 of the planned focal plane P0, the image shift amount on the planned focal plane P0. Becomes x2.

  FIG. 25 is a diagram for explaining conversion from an image shift amount to a defocus amount. In the figure, 402 and 403 are the center of gravity of the distance measuring pupil, P0 is the planned focal plane, P1 is a plane away from the exit pupil plane 90 with respect to the planned focal plane P0, and P2 is exited with the planned focal plane P0 as the reference. It is a surface close to the pupil plane 90 direction. When the plane P1 is the in-focus plane, the amount of deviation of the ray passing through the center of gravity 402, 403 of the distance measuring pupil at the planned focal plane is xP1. Note that the amount of misalignment is defined as + in the upward direction on the paper with reference to the position of the light beam passing through the center of gravity 403. When the plane P2 is the in-focus plane, the amount of deviation of the ray passing through the center of gravity 402, 403 of the distance measuring pupil at the planned focal plane is xP2.

Defocus amounts of the planes P1 and P2 with respect to the planned focal plane P0 are dP1 and dP2. Here, the defocus amount is + in the direction of the exit pupil plane 90 with reference to the planned focal plane P0. In general, assuming that the image shift amount x, the center-of-gravity distance G, and the distance measurement pupil distance d, the defocus amount D is obtained by the following equation.
D = x · d / (G + x) (9)

  Returning again to FIG. 16, the description of step 210 will be continued. The center-of-gravity distance G2 is stored in advance by design values or measured values. The center-of-gravity distance G1 'when vignetting occurs changes in a complex manner depending on conditions such as the type of interchangeable lens, the focusing state, the zooming state, and the presence or absence of a hood. It is impossible in practice to find it. Therefore, the four image shift amounts x11, x12, x21, x22 and the center-of-gravity interval G2 are obtained by calculation.

  As shown in FIG. 24, in the same focus detection area, the two image shift amounts x11, x12 and x21, x22 are the same defocus amount (defocus amount D1 of the focus detection area 101, defocus amount of the focus detection area 102). The focus amount D2) should be obtained. Further, since the positions of the two focus detection areas are on concentric circles with the optical axis as the center on the screen, the vignetting of the focus detection light beams in the two focus detection areas also occurs in the same state.

When the defocus amounts D1 and D2 are obtained from the image shift amounts x11 and x12 and x21 and x22 by the equation (9), the following equation is obtained.
D1 = x11 · d / (G1 ′ + x11) = x12 · d / (G2 + x12) (10)
D2 = x21 · d / (G1 ′ + x21) = x22 · d / (G2 + x22) (11)
The center-of-gravity interval G1 ′ is obtained by modifying Expressions (10) and (11). Here, for the sake of convenience, the center-of-gravity interval G1 ′ obtained from the equation (10) is G11 ′, and the center-of-gravity interval G1 ′ obtained from the equation (11) is G12 ′.
G11 ′ = (G2 + x12) · x11 / x12−x11 (12)
G12 ′ = (G2 + x22) · x21 / x22−x21 (13)

The center-of-gravity interval obtained by the equations (12) and (13) is averaged, and the center-of-gravity interval G1 ′ obtained at the previous focus detection is weighted and averaged to obtain the current center-of-gravity interval G1 ′.
G1 ′ = k1 · (G11 ′ + G12 ′) / 2 + k2 · G10 ′,
k1 + k2 = 1 (14)
In the case of the first focus detection, there is no previous center-of-gravity interval, so the center-of-gravity interval G1 when there is no vignetting is used as G10 ′, or (G11 ′ + G12 ′) / 2 is used as G1 ′. If one or both image shift amounts cannot be detected in either focus detection area, G11 ′ or G12 ′ is adopted instead of (G11 ′ + G12 ′) / 2. Further, when one or both image shift amounts cannot be detected in both focus detection areas, G10 ′ is adopted as G1 ′. The strength of the averaging action can be controlled according to the ratio between the value of the coefficient k1 and the value of the coefficient k2.

In step 220, the defocus amount DEF of the selected focus detection area is calculated based on the corrected center-of-gravity interval G1 ′ obtained by the equation (14). When the focus detection area 101 is selected,
DEF = x11 · d / (G1 ′ + x11) (15)
When the focus detection area 102 is selected,
DEF = x21 · d / (G1 ′ + x21) (16)
In step 230, the process returns.

In the equations (12) and (13), when the image shift amounts x11, x12, x21, and x22 are smaller than the center-of-gravity intervals G1 ′ and G2, the following simplified equations can be used.
G11 ′ = G2 · x11 / x12 (17)
G12 ′ = G2 · x21 / x22 (18)

  As described above, an image shift amount of a pair of images formed by a pair of focus detection light fluxes passing through a distance measuring pupil whose center-of-gravity interval has changed and a pair of focus detections passing through a distance-measuring pupil whose center-of-gravity interval does not change. The changed center-of-gravity interval is obtained based on the ratio of the image displacement amount of the pair of images formed by the light flux.

<< Modification of Embodiment of Invention >>
In this modification, pupil division is performed by a microlens and a light receiving unit disposed behind the microlens. One microlens is provided with one light receiving unit. Although the focus detection pixels shown in FIGS. 5 and 6 include a pair of photoelectric conversion units in one pixel, focus detection can be performed even if only one of the pair of light receiving units is included in one pixel. . For example, instead of the focus detection pixels shown in FIGS. 5 and 6, focus detection pixels 313 and 314 shown in FIGS. 26A and 26B are alternately arranged, and focus detection shown in FIGS. 27A and 27B is performed. By alternately arranging the pixels 315 and 316, focus detection can be performed in the same manner as the focus detection pixels shown in FIGS.

  The focus detection pixel 313 illustrated in FIG. 26A includes one photoelectric conversion unit 16 corresponding to the photoelectric conversion unit 13 illustrated in FIG. 5, and the focus detection pixel 314 illustrated in FIG. 26B is illustrated in FIG. One photoelectric conversion unit 17 corresponding to the photoelectric conversion unit 12 is provided. Further, the focus detection pixel 315 illustrated in FIG. 27A includes one photoelectric conversion unit 18 corresponding to the photoelectric conversion unit 15 illustrated in FIG. 6, and the focus detection pixel 316 illustrated in FIG. One photoelectric conversion unit 19 corresponding to the photoelectric conversion unit 14 shown in FIG.

  In FIG. 28, an imaging element 212 </ b> A in which the focus detection pixels 313 and 314 shown in FIG. 26 are adopted as the first focus detection pixels and the focus detection pixels 315 and 316 shown in FIG. 27 are adopted as the second focus detection pixels is arranged. Show. In FIG. 28, the detection pitch of the image by the focus detection pixels 313 and 314 and the focus detection pixels 315 and 316 is every other pixel. In the imaging device 212A having such a configuration, the configuration of the imaging device is simplified, manufacturing is easy, and cost can be reduced as compared with a case where a pair of photoelectric conversion units is packed in one pixel.

<< Modification of the First Embodiment of the Invention >>
In this modification, pupil division is performed by a re-imaging type pupil division method. FIG. 29 shows the configuration of the re-imaging type pupil division method. The arrangement of the focus detection areas is the same as that shown in FIG. 2, and two re-imaging type pupil division scheme configurations having different ranging pupils for one focus detection area are applied. The re-imaging optical system includes a field mask 371 having apertures 370 and 470, a condenser lens 372, a diaphragm mask 375 having two pairs of aperture openings 373, 374, 473, and 474, and two pairs of re-imaging lenses 376. 377, 476, 477, and the image sensor 379 includes two pairs of light receiving portions 380, 381, 480, 481. The field mask 371 is disposed at or near the planned focal plane of the photographing optical system. The openings 370 and 470 are arranged at the position of one focus detection area in FIG.

  The condenser lens 372 includes a portion corresponding to the field mask opening 370 and a portion corresponding to the field mask opening 470, and the pair of aperture openings 373 and 374 are near the exit pupil of the photographing optical system by the condenser lens 372. Are projected onto a pair of regions 331 and 332 that are symmetrical with respect to the optical axis of the surface 90, and the pair of aperture openings 473 and 474 are formed on the surface 90 near the exit pupil of the photographing optical system by the condenser lens 372. The light is projected onto a pair of regions 341 and 342 that are symmetrical with respect to the optical axis. The pair of regions 331 and 332 and the pair of regions 341 and 342 form a distance measuring pupil. The width in the alignment direction of the ranging pupils 341 and 342 (ranging pupil F value) is set smaller than the width in the alignment direction of the ranging pupils 331 and 332 (ranging pupil F value). This is the same relationship as that of the pupil division type distance measuring pupil (FIGS. 12 and 13).

  The light beams passing through the pair of regions 331 and 332 first form a primary image in the vicinity of the opening 370 of the field mask 371. The primary image formed in the opening 370 of the field mask 371 passes through the condenser lens 372 and the pair of aperture openings 373 and 374, and the light receiving portions 380 and 380 of the image sensor 379 by the pair of re-imaging lenses 376 and 377. Re-imaged as a pair of secondary images on 381. A light beam passing through the pair of regions 341 and 342 first forms a primary image near the opening 470 of the field mask 371. The primary image formed in the opening 470 of the field mask 371 passes through the condenser lens 372, the pair of aperture openings 473, 474, and the light receiving portions 480, 480 of the image sensor 379 by the pair of re-imaging lenses 476, 477. Re-imaged as a pair of secondary images on 481.

  The light intensity distributions of these two pairs of secondary images are converted into electrical image data by the light receiving units 380, 381, 480, 481. By performing image shift calculation processing on the image data, two image shift amounts are calculated for one focus detection area. The same configuration as described above is arranged corresponding to the other focus detection area. In the configuration as described above, image shift amounts having different distance measurement pupil F values are detected for the two focus detection areas. Expressions (12) to (16) can be applied to these four image shift amounts.

  In FIG. 29, the opening 370 and the opening 470 are arranged close to each other, but the optical path is divided by a half mirror or the like between the exit pupil plane and the planned focal plane, and the opening 370 is provided in each optical path. By disposing the focus detection optical system having the focus detection optical system having the opening 470, the focus detection positions can be completely matched.

<< Second Embodiment of the Invention >>
In the second embodiment, the change in the center-of-gravity distance between the distance measurement pupils caused by the vignetting is calculated based on the two image shift amounts obtained based on the focus detection light flux passing through the distance measurement pupil in which the alignment direction of the distance measurement pupils is orthogonal. Obtained by the ratio of Note that pupil division is performed by a microlens and a pair of light receiving units arranged behind the microlens. The configuration of the imaging apparatus is the same as in FIG.

  FIG. 30 shows an example of a focus detection position on the imaging screen, that is, an area (focus detection area, focus detection position) in which an image is sampled on the screen when a focus detection pixel column described later performs focus detection. Focus detection areas 103 and 104 are arranged on the left and right in the horizontal direction across the center 105 on the screen 100. In the focus detection area 103, the image shift direction is the horizontal direction, that is, the focus detection area 103a in which the alignment direction of the distance measurement pupils is the radial direction from the screen center 105, and the image shift detection direction is the vertical direction, that is, the alignment direction of the distance measurement pupils. It consists of a focus detection area 103b in the circumferential direction with respect to the screen center 105. In the focus detection area 104, the image shift direction is the horizontal direction, that is, the focus detection area 104a in which the alignment direction of the distance measurement pupils is the radial direction from the screen center 105, and the image shift detection direction is the vertical direction, that is, the alignment direction of the distance measurement pupils. It consists of a focus detection area 104b in the circumferential direction with respect to the screen center 105. The two focus detection areas 103 and 104 are located on a circumference 103 having a predetermined radius with the screen center 105 as the center.

  FIG. 31 is a front view showing a detailed configuration of the image sensor 212B according to a modification, and is an enlarged view of the vicinity of one focus detection area on the image sensor. The image pickup element 212B has an image pickup pixel 310, the image shift direction is the horizontal direction, that is, the focus detection pixels 321 corresponding to the focus detection area in the radial direction from the screen center 105, and the image shift detection direction is the vertical direction. The focus detection pixels 322 correspond to the focus detection areas in which the distance measurement pupils are arranged in the circumferential direction with respect to the screen center 105. The basic structure of the focus detection pixels 321 and 322 and the principle of pupil division are the same as those of the focus detection pixel 311 described in the first embodiment. The focus detection pixels 321 are arranged every other pixel in the horizontal direction. The focus detection pixels 322 are arranged every other pixel in the vertical direction.

  32 and 33 are front views showing the projection relationship between a pair of photoelectric conversion units on the exit pupil plane. In FIG. 32, the circumscribed circle of the distance measuring pupils 922 and 933 obtained by projecting a pair of photoelectric conversion units from the focus detection pixel 321 onto the exit pupil plane 90 by the microlens is a predetermined aperture F value (when viewed from the imaging plane). This is called a distance measuring pupil F value, here F2.8). A region 901 indicated by a broken line indicates a region corresponding to an aperture value (for example, F2) having an aperture diameter larger than the aperture value F2.8, and includes the distance measuring pupils 922 and 933 therein. The distance between the centers of gravity 952 and 953 of the light beams (focus detection light beams) passing through the distance measurement pupils 922 and 933 in the direction in which the distance measurement pupils 922 and 933 are aligned (horizontal direction in the figure) is G1.

  In FIG. 33, the circumscribed circle of the distance measuring pupils 822 and 833 obtained by projecting the pair of photoelectric conversion units from the focus detection pixel 322 onto the exit pupil plane 90 by the microlens is a predetermined aperture F value ( This is called a distance measuring pupil F value, here F2.8). A region 901 indicated by a broken line indicates a region corresponding to an aperture value (for example, F2) having an aperture diameter larger than the aperture value F2.8, and includes the distance measuring pupils 922 and 933 therein. The distance between the centroids 852 and 853 of the light beams (focus detection light beams) passing through the distance measurement pupils 822 and 833 in the direction in which the distance measurement pupils 822 and 823 are aligned (vertical direction in the figure) is G2 (= G1).

  34 and 35 are front views showing the projection relationship of the exit pupil plane in the state of FIG. 34 and 35 show a state in which a region 903 corresponding to the opening restricting element 98 is added to the states of FIGS. 32 and 33. In FIG. 34, the distance measuring pupil 922 is located by the area 903, and the center of gravity 972 of the light beam (focus detection light flux) passing through the distance measuring pupil 922 restricted by the area 903 is centered from the center of gravity 952 when not being located. It depends on. On the other hand, the distance measuring pupil 933 is not displaced by the region 903, and the position of the center of gravity 953 of the light beam (focus detection light beam) passing through the distance measuring pupil 922 does not change. Accordingly, the distance between the distance measurement pupil centroids 972 and 953 is a centroid distance G1 'that is narrower than the centroid distance G1 when no vignetting occurs.

  In FIG. 35, since vignetting occurs symmetrically in the distance measurement pupils 822 and 823, the center of gravity positions 852 and 853 of the distance measurement pupils 822 and 823 are not changed by the region 903. The interval G2 between the centroids 954 and 955 of the passing light beam (focus detection light beam) does not change.

  With the above configuration, for each of the two focus detection areas 103 and 104 shown in FIG. 30, the image shift amount of the focus detection system in which the distance measurement center of gravity changes due to vignetting, and the distance measurement center of gravity center due to vignetting. And the image shift amount of the focus detection system in which does not change. By applying the formulas (12) to (16) to these four image shift amounts, it is possible to detect the defocus amount based on the data in which the change in the center of gravity interval is corrected.

  In the second embodiment, there is an advantage that image shift detection is possible in two directions orthogonal to each other in the same focus detection area.

<< Modification of Second Embodiment of Invention >>
In this modification, pupil division is performed by a microlens and a light receiving unit disposed behind the microlens. One microlens is provided with one light receiving unit. By applying the focus detection pixels shown in FIG. 26 to the array of focus detection pixels in FIG. 31, it is possible to detect the defocus amount using data in which the change in the center-of-gravity interval is similarly corrected.

<< Another Modification of the Second Embodiment of the Invention >>
In this modification, pupil division is performed by a re-imaging type pupil division method. FIG. 36 shows the configuration of the re-imaging type pupil division method. The arrangement of the focus detection areas is the same as the arrangement shown in FIG. 2, but there are two re-imaging type pupil division schemes having distance measurement pupils with different alignment directions of the distance measurement pupils for one focus detection area. Applied. The re-imaging optical system includes a field mask 371 having apertures 370 and 570, a condenser lens 372, a diaphragm mask 375 having two pairs of aperture openings 373, 374, and 573, 574, and two pairs of re-imaging lenses 376 and 377. , 576, 577, and the image sensor 379 includes two pairs of light receiving portions 380, 381, 580, 581. The field mask 371 is disposed at or near the planned focal plane of the photographing optical system.

  The openings 370 and 570 are arranged at the position of one focus detection area shown in FIG. 2, the opening 370 is the focus detection area 103a (or 104a) in FIG. 30, and the opening 570 is the focus detection area shown in FIG. 103b (or 104b). The pair of aperture openings 373 and 374 are projected by the condenser lens 372 onto a pair of regions 331 and 332 that are symmetrical with respect to the optical axis of the surface 90 in the vicinity of the exit pupil of the photographing optical system. The openings 573 and 574 are projected by the condenser lens 372 onto a pair of regions 351 and 352 that are symmetrical with respect to the optical axis of the surface 90 in the vicinity of the exit pupil of the photographing optical system. The pair of areas 331 and 332 and the pair of areas 351 and 352 form a distance measuring pupil. The alignment direction of the distance measurement pupils 331 and 332 and the alignment direction of the distance measurement pupils 331 and 332 are orthogonal to each other, and have the same relationship as the relationship between the distance measurement pupils shown in FIGS.

  The light beams passing through the pair of regions 331 and 332 first form a primary image in the vicinity of the opening 370 of the field mask 371. The primary image formed in the opening 370 of the field mask 371 passes through the condenser lens 372 and the pair of aperture openings 373 and 374, and the light receiving portions 380 and 380 of the image sensor 379 by the pair of re-imaging lenses 376 and 377. Re-imaged as a pair of secondary images on 381. A light beam passing through the pair of regions 351 and 352 first forms a primary image near the opening 570 of the field mask 371. The primary image formed in the opening 570 of the field mask 371 passes through the condenser lens 372, the pair of aperture openings 573, 574, and the light receiving portions 580 of the image sensor 379 by the pair of re-imaging lenses 576, 577. Re-imaged as a pair of secondary images on 581. The light intensity distributions of these two pairs of secondary images are converted into electrical image data by the light receiving units 380, 381, 580, 581. By performing image shift calculation processing on the image data, two image shift amounts are calculated for one focus detection area. The same configuration as described above is arranged corresponding to the other focus detection area.

  In the configuration as described above, the image shift amount of the focus detection system in which the distance measurement center of gravity center changes due to vignetting and the image of the focus detection system in which the distance measurement center of gravity center does not change due to vignetting for two focus detection areas. The amount of deviation is required. By applying the formulas (12) to (16) to these four image shift amounts, it is possible to detect the defocus amount using data in which the change in the center of gravity interval is corrected.

<< Third Embodiment of the Invention >>
The ratio of the center of gravity of the distance measurement pupil caused by vignetting is determined by the ratio of the two image shift amounts obtained based on the focus detection light flux passing through the distance measurement pupil whose range pupil F value has changed by changing the aperture of the photographing optical system. A third embodiment in which a change is obtained will be described. In this embodiment, pupil division is performed by a microlens and a pair of light receiving units arranged behind the microlens. In this embodiment, the configuration of the imaging apparatus is the same as that shown in FIG. 1, and the arrangement of focus detection positions is the same as that shown in FIG.

  FIG. 37 is a front view showing a detailed configuration of the image sensor 212C. This imaging element 212C is obtained by omitting the focus detection pixel 312 from the configuration shown in FIG. The relationship between the distance measuring pupils on the exit pupil plane is the same as the relationship shown in FIG.

  38 and 39 are front views showing the distance-measuring pupil relationship on the exit pupil plane in the state of FIG. 38 and 39 show a state in which a region 903 corresponding to the opening restriction element 98 is added to the state of FIG. In FIG. 38, the distance measurement pupil 922 is located by the region 903, and the center of gravity 972 of the light beam (focus detection light beam) passing through the distance measurement pupil 922 restricted by the region 903 is centered from the center of gravity 952 when not being located. It depends on. On the other hand, the distance measuring pupil 933 is not displaced by the region 903, and the position of the center of gravity 953 of the light beam (focus detection light beam) passing through the distance measuring pupil 922 does not change. Therefore, the distance between the distance measurement pupil centroids 972 and 953 is a centroid distance G1 'narrower than the centroid distance G1 when no vignetting occurs.

  In FIG. 39, the aperture diameter of the photographing optical system is reduced (the aperture value is increased) so that the influence of vignetting due to the region 903 is eliminated, and the range is indicated by a broken line 801. The centroids 982 and 983 of the light beams (focus detection light beams) passing through the distance measuring pupils 922 and 933 limited by the region 801 are more centered than the centroids 952 and 953 when they are not located. The gap G3 between the centroids 982 and 983 can be obtained and memorized in advance by measurement or calculation because no squealing occurs in aperture limiting elements other than the diaphragm.

With the above configuration, the image shift amount when the aperture stop of the optical system is not stopped (the state of the distance measuring pupil in FIG. 38) and the optical system for each of the two focus detection areas 101 and 102 shown in FIG. The image shift amount in the state where the aperture of the aperture is stopped (the state of the distance measuring pupil in FIG. 39) is obtained. By applying the formulas (12) to (16) to these four image shift amounts, it is possible to detect the defocus amount using data in which the change in the center of gravity interval is corrected.

  FIG. 40 is a flowchart showing the processing of steps 120 to 130 in FIG. 15 according to the third embodiment. In step 400, the data of the focus detection pixel columns in the focus detection areas 101 and 102 are read with the aperture diameter set to the shooting aperture value, and focus detection calculation processing (correlation calculation processing) is performed on each of these data. Image shift amounts x11 and x21 in the focus detection areas 101 and 102 are calculated. In step 410, the data of the focus detection pixel columns in the focus detection areas 101 and 102 are read out with the aperture diameter reduced to the aperture diameter of the interchangeable lens that eliminates the pre-stored vignetting, and each of these data is subjected to focus detection. Calculation processing (correlation calculation processing) is performed, and image shift amounts x12 and x22 in the focus detection areas 101 and 102 are calculated.

  In step 420, the distance measurement pupil center-of-gravity interval G1 'with the aperture diameter set to the photographing aperture value is calculated by applying the equations (12) to (14) to the four image shift amounts. In the equations (12) and (13), the center-of-gravity interval G3 in a state where the aperture is reduced to a predetermined value is used instead of the center-of-gravity interval G2. In step 430, the defocus amount DEF of the focus detection area selected by the equation (15) or the equation (16) is calculated based on the corrected center-of-gravity interval G1 '. Thereafter, the process returns at step 440.

  According to the third embodiment, there is an advantage that a plurality of focus detection pixel arrays are not required in one focus detection area.

<< Modification of Third Embodiment of Invention >>
In this modification, pupil division is performed by a microlens and a light receiving unit disposed behind the microlens. One microlens is provided with one light receiving unit. By applying the focus detection pixels shown in FIG. 26 to the array of focus detection pixels in FIG. 37, the image sensor 212D shown in FIG. 41 can be configured. Even in such a configuration, it is possible to obtain data in which the change in the distance between the center of gravity of distance measurement is corrected by changing the aperture diameter of the aperture, and the defocus amount can be detected based on these data.

<< Another Modification of the Third Embodiment of the Invention >>
In this modification, pupil division is performed by a re-imaging type pupil division method. The configuration of the re-imaging optical system is such that only the focus detection optical system corresponding to the opening 370 exists in FIG. Even in such a configuration, the change in the center-of-gravity interval is corrected by applying Equations (12) to (16) to four image shift amounts obtained by varying the aperture diameter of the photographing optical system. The defocus amount can be detected based on the data.

<< Other modifications >>
In the imaging device described above, an example in which the imaging pixel includes a Bayer color filter is shown. However, the configuration and arrangement of the color filter are not limited to this, and for example, complementary color filters (green: G, yellow: Ye, Magenta: Mg, cyan: Cy) may be employed. The focus detection pixel is arranged at a pixel position where cyan and magenta (including a blue component whose output error is relatively inconspicuous) should be arranged.

  In the image pickup device described above, an example in which the focus detection pixel is not provided with a color filter is shown. However, the present invention is applied even when one filter (for example, a green filter) is provided among the color filters of the same color as the image pickup pixel. can do.

  In the above-described imaging device, an example in which focus detection pixels are used instead of imaging pixels as part of the imaging pixels has been described, but all pixels may be configured with focus detection pixels.

  In the image pickup apparatus (camera) shown in FIG. 1, an example in which the image pickup device is used for both focus detection and image pickup has been shown, but the focus detection image pickup device and the image pickup image pickup device are provided separately to divide the photographing light flux. Thus, the configuration may be such that the imaging light flux is guided to each imaging element, and focus detection and imaging are performed.

  In the flowchart shown in FIG. 15, the corrected image data is stored in the memory card. However, the corrected image data is displayed on a back monitor screen (not shown) provided on the back of the electronic viewfinder or the body. May be.

  The above-described imaging device can be formed as a CCD image sensor or a CMOS image sensor. The imaging apparatus is not limited to a digital still camera or a film still camera in which an interchangeable lens is mounted on the camera body, and can also be applied to a lens-integrated digital still camera, a film still camera, and a video camera. It can also be applied to a small camera module built in a mobile phone or a surveillance camera. Alternatively, the present invention can be applied to a focus detection device other than a camera, a distance measuring device, or a stereo distance measuring device.

  As described above, according to one embodiment, the conversion coefficient for converting the image shift amount into the defocus amount can be accurately calculated with simple calculation without requiring a huge amount of data and complicated calculation processing of the optical system. In addition, it can be easily applied to various optical systems having different configurations.

The figure which shows the structure of one embodiment Diagram showing the focus detection position on the imaging screen Front view showing detailed configuration of image sensor The figure which shows the structure of an imaging pixel The figure which shows the structure of a 1st focus detection pixel. The figure which shows the structure of a 2nd focus detection pixel. Diagram showing spectral characteristics of green, red and blue pixels Diagram showing spectral characteristics of focus detection pixels Cross section of imaging pixel Cross section of focus detection pixel The figure for demonstrating the focus detection method by the pupil division system using a micro lens Front view showing the projection relationship of the photoelectric conversion unit of the first focus detection pixel on the exit pupil plane Front view showing the projection relationship of the photoelectric conversion unit of the second focus detection pixel on the exit pupil plane A graph showing the intensity distribution (light quantity) of the image signal of the focus detection pixel at the focus detection position around the screen on the vertical axis and the position of the focus detection pixel on the horizontal axis. 1 is a flowchart showing the operation of the digital still camera (imaging device) shown in FIG. The flowchart which shows the detail of the image shift amount calculation process in step 130 of FIG. 16 is a flowchart showing details of the focus detection calculation process in step 200 of FIG. Diagram explaining correlation calculation processing Front view showing a pair of photoelectric conversion unit projection relationship of the first focus detection pixel on the exit pupil plane Front view showing a pair of photoelectric conversion unit projection relationship of the second focus detection pixels on the exit pupil plane The figure explaining the vignetting of the distance measuring pupil around the screen Front view showing the projection relationship of the exit pupil plane of the first focus detection pixel in the state shown in FIG. Front view showing the projection relation of the exit pupil plane in the state shown in FIG. 21 of the second focus detection pixel. The figure which shows the relationship between the distance pupil center-of-gravity interval and the amount of image gap Diagram for explaining conversion from image shift amount to defocus amount The figure which shows the structure of the modification of a 1st focus detection pixel. The figure which shows the structure of the modification of a 2nd focus detection pixel. Front view showing a detailed configuration of an image sensor of a modification Diagram showing the configuration of the re-imaging pupil division method The figure which shows the focus detection position on the imaging screen Front view showing a detailed configuration of an image sensor of a modification Front view showing the projection relationship of a pair of photoelectric conversion units on the exit pupil plane Front view showing the projection relationship of a pair of photoelectric conversion units on the exit pupil plane The front view which shows the projection relationship of the exit pupil plane in the state of FIG. The front view which shows the projection relationship of the exit pupil plane in the state of FIG. Diagram showing the configuration of the re-imaging pupil division method Front view showing a detailed configuration of the image sensor of the modification FIG. 21 is a front view showing a distance measuring pupil relationship on the exit pupil plane in the state of FIG. FIG. 21 is a front view showing a distance measuring pupil relationship on the exit pupil plane in the state of FIG. The flowchart which shows the process of steps 120-130 of FIG. 15 in 3rd Embodiment. The figure which shows the detailed structure of the image pick-up element of a modification.

Explanation of symbols

212, 212A, 212B, 212C, 212D Image sensor 214 Body drive control device 216 Liquid crystal display element 219 Memory card

Claims (13)

A first pair of images formed by a first pair of luminous fluxes respectively passing through a first pair of regions of the exit pupil of the optical system, and a second pair of regions of the exit pupil of the optical system, respectively. And a second pair of images formed by the second pair of luminous fluxes, respectively, and a first pair of image signals corresponding to the first pair of images and the second pair of images and the second pair of images, respectively. First light receiving means for outputting two pairs of image signals ;
First image shift amount detection means for detecting a first image shift amount based on the first pair of image signals and a second image shift amount based on the second pair of image signals ;
First center-of-gravity interval calculation means for calculating the center-of-gravity interval of the first pair of regions based on the center-of-gravity interval of the second pair of regions, the first image shift amount, and the second image shift amount. When,
Defocus amount calculating means for calculating a defocus amount based on the center of gravity interval calculated by the first center of gravity interval calculating means and the first image shift amount;
The focus detection apparatus according to claim 1, wherein a center-of-gravity interval between the first pair of regions is larger than a center-of-gravity interval between the second pair of regions . The focus detection apparatus according to claim 1,
The focus detection device includes a first focus detection area at a position away from the center of the shooting screen by a predetermined distance within a shooting screen of the optical system, and a second position at a position away from the center of the shooting screen by the predetermined distance. A focus detection area,
The focus detection device includes a third pair of images formed by a third pair of light beams respectively passing through a third pair of regions of the exit pupil of the optical system, and a fourth of the exit pupil of the optical system. And a fourth pair of images formed by a fourth pair of light beams respectively passing through the pair of regions, and a third pair corresponding to the third pair of images and the fourth pair of images, respectively. A second light receiving means for outputting a pair of image signals and a fourth pair of image signals; a third image shift amount based on the third pair of image signals; and a fourth pair of image signals. A second image shift amount detecting means for detecting a fourth image shift amount based on the second image shift amount; a center-of-gravity interval of the fourth pair of regions; a third image shift amount; and a fourth image shift amount. And a second center-of-gravity interval calculating means for calculating the center-of-gravity interval of the third pair of regions based on:
The centroid spacing of the third pair of regions is greater than the centroid spacing of the fourth pair of regions,
The first light receiving means receives the first pair of images and the second pair of images in the first focus detection area,
The second light receiving means receives the third pair of images and the fourth pair of images in the second focus detection area,
The defocus amount calculating means includes an average value of the centroid distance calculated by the first centroid distance calculating means and the centroid distance calculated by the second centroid distance calculating means, and the first image. A focus detection apparatus that calculates a defocus amount based on a shift amount . The focus detection apparatus according to claim 1 ,
The first light receiving means receives the first pair of images formed by the first pair of light beams respectively passing through the first pair of regions, and outputs the first pair of image signals. The second pair of image signals are received by receiving the second pair of images formed by the first light receiving unit to output and the second pair of light beams respectively passing through the second pair of regions. And a second light receiving unit that outputs a focus detection device. The focus detection apparatus according to claim 3 ,
The focus detection device includes a first focus detection area at a position away from the center of the shooting screen by a predetermined distance within a shooting screen of the optical system, and a second position at a position away from the center of the shooting screen by the predetermined distance. A focus detection area,
The focus detection device receives a third pair of images formed by a third pair of light beams respectively passing through a third pair of regions of the exit pupil of the optical system, and receives a third pair of image signals. And receiving a fourth pair of images formed by a fourth pair of light fluxes that respectively pass through a third pair of light receiving sections that output and a fourth pair of regions of the exit pupil of the optical system. A second light receiving unit having a fourth light receiving unit for outputting the image signal of the second, a fourth image shift based on the third image shift amount based on the third pair of image signals and the fourth pair of image signals. Based on the second image displacement amount detecting means for detecting the image displacement amount of each of the second pair of regions, the center-of-gravity interval of the fourth pair of regions, the third image displacement amount, and the fourth image displacement amount. Second centroid distance calculating means for calculating the centroid distance of the third pair of regions,
The centroid spacing of the third pair of regions is greater than the centroid spacing of the fourth pair of regions,
The first light receiving means receives the first pair of images and the second pair of images in the first focus detection area,
The second light receiving means receives the third pair of images and the fourth pair of images in the second focus detection area,
The defocus amount calculating means includes an average value of the centroid distance calculated by the first centroid distance calculating means and the centroid distance calculated by the second centroid distance calculating means, and the first image. A focus detection apparatus that calculates a defocus amount based on a shift amount . The focus detection apparatus according to claim 1 ,
A diaphragm control means for controlling the diaphragm aperture of the optical system to at least a first aperture diameter and a second aperture diameter smaller than the first aperture diameter;
The first light receiving means is formed by the first pair of light beams respectively passing through the first pair of regions when the stop opening is controlled to the first opening diameter by the stop control means. Receiving the first pair of images and outputting the first pair of image signals, and when the diaphragm opening is controlled to the second opening diameter by the diaphragm control means, A focus detection apparatus that receives the second pair of images formed by the second pair of light beams respectively passing through the pair of regions and outputs the second pair of image signals . The focus detection apparatus according to claim 5 ,
The focus detection device includes a first focus detection area at a position away from the center of the shooting screen by a predetermined distance within a shooting screen of the optical system, and a second position at a position away from the center of the shooting screen by the predetermined distance. A focus detection area,
The focus detection device includes a third pair of images formed by a third pair of light beams respectively passing through a third pair of regions of the exit pupil of the optical system and a fourth of the exit pupil of the optical system. A fourth pair of images formed by a fourth pair of light beams respectively passing through the pair of regions, and receiving a third pair of images corresponding to the third pair of images and the fourth pair of images, respectively. A second light receiving means for outputting a pair of image signals and a fourth pair of image signals; a third image shift amount based on the third pair of image signals; and a second pair of image signals based on the fourth pair of image signals. A second image deviation amount detecting means for detecting each of the four image deviation amounts, a center-of-gravity interval of the fourth pair of regions, the third image deviation amount, and the fourth image deviation amount, Second centroid distance calculating means for calculating a centroid distance of the third pair of regions,
The second light receiving means is formed by the third pair of light beams respectively passing through the third pair of regions when the diaphragm opening is controlled to the first opening diameter by the diaphragm control means. Receiving the third pair of images and outputting the third pair of image signals, and when the stop opening is controlled to the second opening diameter by the stop control means, Receiving the fourth pair of images formed by the fourth pair of light beams respectively passing through the pair of regions, and outputting the fourth pair of image signals;
The centroid spacing of the third pair of regions is greater than the centroid spacing of the fourth pair of regions,
The first light receiving means receives the first pair of images and the second pair of images in the first focus detection area,
The second light receiving means receives the third pair of images and the fourth pair of images in the second focus detection area,
The defocus amount calculating means includes an average value of the centroid distance calculated by the first centroid distance calculating means and the centroid distance calculated by the second centroid distance calculating means, and the first image. A focus detection apparatus that calculates a defocus amount based on a shift amount . A light receiving means for receiving a pair of images formed by a pair of light beams passing through a pair of regions of the exit pupil of the optical system and outputting a pair of image signals corresponding to the pair of images;
Stop control means for controlling the aperture of the optical system to at least a first aperture and a second aperture smaller than the first aperture;
A first image shift amount is detected based on the pair of image signals when the stop opening is controlled to the first opening diameter by the stop control means, and the stop opening is detected by the stop control means. Image displacement amount detection means for detecting a second image displacement amount based on the pair of image signals when controlled to the aperture diameter of
Based on the center-of-gravity interval of the pair of regions, the first image shift amount, and the second image shift amount when the stop aperture is controlled to the second aperture diameter, the stop aperture is the first aperture. Centroid interval calculating means for calculating the centroid interval of the pair of regions when controlled to the opening diameter of
A focus detection apparatus comprising: a defocus amount calculating unit that calculates a defocus amount based on the center of gravity interval calculated by the center of gravity interval calculating unit and the first image shift amount . A first focus detection area extending in a radial direction from the center of the shooting screen and a position perpendicular to the first focus detection area at a predetermined distance from the center of the shooting screen in the shooting screen of the optical system. A focus detection device having a second focus detection area,
A first pair of images formed by a first pair of light beams respectively arranged in a direction corresponding to the first focus detection area and passing through a first pair of regions of the exit pupil of the optical system, respectively. A first focus detection pixel array that receives light and outputs a first pair of image signals corresponding to the first pair of images, and is arranged in a direction corresponding to the second focus detection area; Each of the second pair of images formed by the second pair of light fluxes respectively passing through the second pair of regions of the exit pupil of the second pupil, and a second pair of images corresponding to the second pair of images First light receiving means having a second focus detection pixel row for outputting an image signal;
First image shift amount detection means for detecting a first image shift amount based on the first pair of image signals and a second image shift amount based on the second pair of image signals;
First center-of-gravity interval calculation means for calculating the center-of-gravity interval of the first pair of regions based on the center-of-gravity interval of the second pair of regions, the first image shift amount, and the second image shift amount. When,
A focus detection device comprising: a defocus amount calculation unit that calculates a defocus amount based on the center of gravity interval calculated by the first center of gravity interval calculation unit and the second image shift amount. . The focus detection apparatus according to claim 8 , wherein
The focus detection device includes a third focus detection area and a third focus that extend in a radial direction from the center of the photographing screen to a position separated from the center of the photographing screen by the predetermined distance within the photographing screen of the optical system. A fourth focus detection area extending perpendicular to the detection area,
The focus detection device is arranged in a direction corresponding to the third focus detection area, and is formed by a third pair of light beams respectively passing through a third pair of regions of the exit pupil of the optical system. Are arranged in a direction corresponding to the fourth focus detection area and a third focus detection pixel array for receiving a pair of images and outputting a third pair of image signals. A fourth focus detection pixel array for receiving a fourth pair of images formed by a fourth pair of light beams respectively passing through a fourth pair of regions and outputting a fourth pair of image signals; And a second image that detects a third image shift amount based on the third pair of image signals and a fourth image shift amount based on the fourth pair of image signals, respectively. Deviation amount detection means, the center-of-gravity distance of the fourth pair of regions, the third image deviation amount, and the fourth image Based on les amount and, further comprising a second centroid distance calculating means for calculating the centroid distance of the third pair of regions,
The defocus amount calculation means includes an average value of the centroid distance calculated by the first centroid distance calculation means and the centroid distance calculated by the second centroid distance calculation means, and the second image. A focus detection apparatus that calculates a defocus amount based on a shift amount . The focus detection apparatus according to claim 1, 3, 5, 7, or 8,
  The light receiving means includes a focus detection pixel that receives the first pair of images, a focus detection pixel that receives the second pair of images, and an imaging pixel that receives the image by the optical system. A focus detection apparatus comprising two-dimensionally arranged image sensors. The focus detection apparatus according to claim 2, 4, 6 or 9,
  The first light receiving unit and the second light receiving unit include a focus detection pixel that receives the first pair of images, a focus detection pixel that receives the second pair of images, and the third An imaging in which focus detection pixels that receive the pair of images, focus detection pixels that receive the fourth pair of images, and imaging pixels that receive the image by the optical system are arranged in a two-dimensional manner A focus detection device comprising an element. An imaging apparatus comprising a focus detection device according to any one of claims 1 to 7
The light receiving means is configured by two-dimensionally arranging focus detection pixels that receive an image of a light flux passing through the plurality of region pairs and imaging pixels that receive an image of the optical system,
Display means for displaying a captured image based on a signal obtained by the imaging pixel;
An image pickup apparatus comprising: a recording unit that records a picked-up image based on a signal obtained by the image pickup pixel. An imaging apparatus comprising a focus detection device according to any one of claims 1 to 7
An imaging light receiving means for outputting a signal corresponding to an image formed by the optical system;
Display means for displaying a captured image based on an output signal of the imaging light receiving means;
An imaging apparatus comprising: a recording unit that records a captured image based on an output signal of the imaging light receiving unit.

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